Size effect of (Al2O3–Y2O3)/YSZ micro-laminated coating on high-temperature oxidation resistance

Abstract

The size effect of structure plays an important role in the high-temperature oxidation and spallation resistance of micro-laminated coating on alloy substrate. In this study, (Al2O3–Y2O3)/YSZ micro-laminated coatings with different thickness ratios and layer numbers were prepared on MCrAlY alloy by electrolytic deposition and microwave sintering under pressure. The oxidation and spallation resistance of the micro-laminated coatings were investigated by cyclic oxidation tests in air at 1050°C for 200h. Results indicate that both oxidation resistance and spallation resistance of the coating have been improved significantly, by increasing the thickness ratio of YSZ layer to Al2O3–Y2O3 layer and layer number in a specific range. In such micro-laminated coating, increasing the thickness ratio of YSZ layer to Al2O3–Y2O3 layer can improve the apparent thermal expansion coefficient of coating and decrease the thermal stresses. While, increasing the layer number can extend the crack propagation paths and improve the plasticity and fracture toughness. They can improve the mechanical properties of micro-laminated coating and exhibit excellent cracking and spallation resistance. This would give rise to the beneficial effects on suppressing the oxygen inward diffusion and consequently improve the high-temperature oxidation resistance of micro-laminated coating. Such size effect would provide reference values in the structural design of micro-laminated coating in high-temperature application.